From: Curt Sampson <cjs@...>
Date: 2005-04-13T15:53:02+09:00
Subject: Re: Scope in Method Definitions

On Wed, 13 Apr 2005, Gennady Bystritsky wrote:

> Oh, yes, a block is used to define a class body, I see. However, "def"
> syntax prevents "foo" from being treated as a closure participant. At
> least, it is how it looks to me ;-).

Bingo! After a bit more playing, it looks like the "class" statement
does this too.

This is not so hard to live with, once you know. The problem is, the
language makes finding out this stuff so darn tough.

If you want to see what this was all about, I've appended a nifty little
bit of code. (I'm using it with a factory that stores Classes, and
later instantiates them; this saves me having to store parameters for
new as well.) It took me quite some time to work out that I had to use
define_method instead of def.

cjs
-- 
Curt Sampson  <cjs@cynic.net>   +81 90 7737 2974   http://www.NetBSD.org
      Make up enjoying your city life...produced by BIC CAMERA


# $Id: curry.rb,v 1.1 2005/04/13 05:41:38 cjs Exp $

require 'test/unit/testcase'

def curryclass(klass, *curried_args)
     curried_class = Class.new(klass) {
 	def initialize(*args)
 	    super_args = curried_args + args
 	    super(*super_args)
 	end
     }
     curried_class
end

class TC_curryclass < Test::Unit::TestCase

     class AddPair
 	def initialize(a, b)
 	    @value = a + b
 	end
 	attr_reader :value
     end

     AddTwoAndFour = curryclass(AddPair, 2, 4)

     AddTwo = curryclass(AddPair, 2)

     def FAILING test_curryclass
 	assert_equal(5, self.class::AddPair.new(2, 3).value)
 	assert_equal(6, self.class::AddTwoAndFour.new.value)
 	assert_equal(7, self.class::AddTwo.new(5).value)
     end

     def test_nothing
     end

end